Improve daterange selection for changes

[harriebird]

Proposed changes

This improves the selection of date ranges for the generation of changes using the DateRangeField.
This solves issue #11846.

Example image:

Checklist

• Lint and unit tests pass locally with my changes.
• I have added tests that prove my fix is effective or that my feature works.
• I have added documentation to describe my feature.
• I have squashed my commits into logic units.
• I have described the changes in the commit messages.

Other information

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.59%. Comparing base (6aee586) to head (faf1e28).
Report is 2235 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11894      +/-   ##
==========================================
- Coverage   90.82%   90.59%   -0.23%     
==========================================
  Files         554      577      +23     
  Lines       57306    58827    +1521     
  Branches     9122     9392     +270     
==========================================
+ Hits        52046    53297    +1251     
- Misses       3640     3837     +197     
- Partials     1620     1693      +73     

Files	Coverage Δ
weblate/trans/forms.py	88.08% <100.00%> (+0.21%)	⬆️
weblate/trans/tests/test_changes.py	100.00% <100.00%> (ø)
weblate/trans/tests/test_reports.py	100.00% <100.00%> (ø)
weblate/trans/views/changes.py	65.78% <100.00%> (+1.45%)	⬆️

... and 328 files with indirect coverage changes

[nijel]

Please revert the changes here as well, reports need period to be provided.

[harriebird]

Reverted the changes for checking if the form.cleaned_data["period"] is None.

[nijel]

This introduced regression: #11954